Endocrine gland

ENDOCRINE GLANDS

are ductless, well-vascularized glands that release hormones directly into the blood or lymph

Help regulate:

• Chemical composition and volume of internal

• environment (interstitial fluid)

• Metabolism and energy

• Contraction of smooth and cardiac muscle fibers

• Glandular secretions

• Some immune system activities

Control growth and development:

• Regulate operation of reproductive system

• Help establish circadian rhythms

Hormones

- exert their effects on target organs or tissues.

- are secreted when there is a need for their effects.

Regulation of ____ Secretion:

• each has a specific stimulus for secretion.

• The secretion of _____ is regulated by negative feedback mechanisms. As the ____exerts its effects, the stimulus for secretion is reversed, and Secretion of the hormone decreases.

Amines

structural variations of the amino acid tyrosine; thyroxine, epinephrine.

Proteins

Chains of amino acids; peptides are short chains. Insulin, GH, glucagon are proteins; ADH and oxytocin are peptides

Steroids

made from cholesterol; cortisol, aldosterone, estrogen, testosterone

hypothalamus

is a neuroendocrine organ

Posterior Pituitary (Neurohypophysis)

Stores hormones produced by the hypothalamus

Antidiuretic hormone (ADH)

- stimulates the kidney tubules to reabsorb and conserve water, resulting in small volumes of highly concentrated urine and decreased plasma osmolality.

• Hyposecretion results in diabetes insipidus.

- is released in response to high solute concentrations in the blood and inhibited by low solution concentrations in the blood.

Oxytocin (OT)

stimulates contraction of myometrium of uterus during labor and release of milk from mammary glands

Anterior Pituitary (Adenohypophysis)

secretions are regulated by releasing hormones from the hypothalamus

Growth hormone (GH)

- is an anabolic hormone that stimulates growth of all body tissues but especially skeletal muscle and bone.

- mobilizes fats, stimulates protein synthesis, and inhibits glucose uptake and metabolism.

Thyroid-stimulating hormone (TSH)

promotes normal development and activity of the thyroid gland

Adrenocorticotropic hormone (ACTH)

stimulates the adrenal cortex to release corticosteroids.

Prolactin (PRL)

Promotes milk production in humans

Follicle-stimulating hormone (FSH)

- In women:

initiates development of ova in ovarian follicles and secretion of estrogen by follicle cells.

In men:

initiates sperm development in the testes

Luteinizing hormone (LH)

In women: stimulates ovulation, transforms mature follicle into corpus luteum and stimulates secretion of progesterone.

In men:

stimulates secretion of testosterone by the testes

Thyroxine (T4) and triiodothyronine (T3)

- Increase use of all food types for energy protein synthesis.

- Necessary for normal physical, mental, and sexual development

Graves’ disease

Is the most common cause of hyperthyroidism

Cretinism

Is the hyposecretion; in infants and myxedema in adults.

Calcitonin

- produced by parafollicular cells of the thyroid gland in response to rising resorption and enhancing calcium deposit in bone.

- It depresses blood calcium levels by inhibiting bone matrix resorption and enhancing calcium deposit in bone.

Parathyroid hormone (PTH)

increases reabsorption of calcium and phosphate from bones to the blood; increases absorption of calcium and phosphate by the small intestine; increases resorption of calcium and excretion of phosphate by the kidneys, and activates vitamin D.

Hyperparathyroidism

- results in hypercalcemia and all its effects and in extreme bone wasting.

- leads to hypocalcemia, evidenced by tetany and respiratory paralysis

Pancreas

- is both an exocrine and an endocrine gland.

- Islets of Langerhans (endocrine portion) contain alpha cells and beta cells.

Glucagon

- secreted by alpha cells.

- Stimulates liver to change glycogen to glucose increases use of fats and amino acids for energy.

Insulin

- secreted by beta cells.

- Increases use of glucose by cells to produce energy; stimulates liver and muscles to change glucose to glycogen; increases cellular intake of fatty acids and amino acids to use for synthesis of lipids and proteins.

Hyposecretion of ______ results in diabetes mellitus;

cardinal signs are polyuria, polydipsia, and polyphagia

Adrenal Glands

- The paired adrenal (suprarenal) glands superior to and

the kidneys.

- Each has two functional portions, the out adrenal cortex and the inner adrenal medulla

Adrenal Medulla

- produces catecholamines (epinephrine and norepinephrine) in response to sympathetic nervous system stimulation.

- Its catecholamines enhance and prolong the fight-or- flight response to short-term stressors.

Adrenal Cortex

– produces mineralocorticoids, glucocorticoids, and very small amounts of sex hormones

Mineralocorticoids

- (primarily aldosterone)

- regulate sodium ion reabsorption and potassium ion excretion by the kidneys.

Sodium ion

reabsorption leads to water reabsorption, and increases in blood volume and blood pressure

Glucocorticoids (primarily cortisol)

- are importantmetabolic hormones help the body resist stressors by increasing blood glucose, fatty acid and amino acid levels, and blood pressure.

- High levels of ______ depress the immune system and the inflammatory response

Ovaries

release two main hormones (estrogen and progesterone)

Estrogen

- Promotes maturation of ovum, stimulates growth of blood vessels in endometrium; stimulates

development of secondary sex characteristics: growth of duct system of mammary glands, growth of uterus, fat deposition.

- Promotes closure of epiphyses of long bones; lowers blood levels of cholesterol and triglycerides.

Progesterone

- produced by the corpus luteum.

- Promotes storage of glycogen and further growth of blood vessels in the endometrium, promotes growth of secretory cells of mammary glands.

Testes

begin to produce testosterone and inhibin.

Testosterone

- produced by interstitial cells.

- Promotes maturation of sperm in testes; stimulates development of secondary sex characteristics: growth of reproductive organs, facial and body hair, larynx, skeletal muscles; promotes closure of epiphyses of long bones.

Inhibin

produced by sustentacular cells. Inhibits secretion of FSH to maintain a constant rate of sperm production.

Pineal gland

Its primary hormone is melatonin, which influences daily rhythms an may have an antigonadotrophic effect in humans.

Thymus gland

- is located in the upper thorax, declines in size and function with age.

- Its hormones, thymosins, hymic factor, and thymopoietins, are important to the normal development of the immune response.

Addison’s disease

Hypoactivity of the adrenal cortex results

Hypersecretion

- causes gigantism in children and acromegaly in adults

- in children causes pituitary dwarfism.

- can result in aldosteronism, Cushing's syndrome and adrenogenital syndrome.

Hyperparathyroidism

- results in hypercalcemia. and all its effects and in extreme bone wasting.

- leads to hypocalcemia, evidenced by tetany and respiratory paralysis.